Variable-contact device



May 5, 1925. 1 1,536,321

W. O. AMSLER VARlABLE CONTACT DEVI CE Filed April 12. 1925 Patented May 5, 1925.

UNITED STATES WALTER O. AMSLER, OF PITTSBURGH, PENNSYLVANIA.

VARIABLE-CONTACT DEVICE.

Application filed April 12, .1923. Serial No. 631,535.

To all who m, it mag concern:

Be it known that I, WALTER O. AMsLnR, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, haveinvented certain new and useful Improvements in Variable-Contact Devices, of which the following is a specification.

This" invention is for a variable contact device for use in varying the resistance or inductance in a given circuit, or in any other apparatus involving the use of a variable contact.

The invention has for its principal objects to provide a device of simple construction, capable of very accurate adjustment, and designed to eifect relatively small increments of variation in a positive and efficient manner, insuring good contact, and in which the parts are subject to minimum wear.

The invention may be readily understood by reference to the accompanying drawings, in which:

Fig. 1 is a top plan view of a device embodying my invention;

Fig. 2 is a transverse section in the plane of line IIII of Fig. 1;

Fig. 3 is a side view of the structure shown in Fig. 1;

Figs. 4, 5 and 6 are views showing modified forms of conducting or resistance elements;

Fig. 7 is a wiring diagram indicative of the use of the device as a rheostat; and

Fig. 8 is a similar view indicating the application of the invention to'a potentiometer.

In the drawings, which are illustrative of one embodiment of the invention, 5 designates a base of insulating material having a cylinder 6 fixed thereto by any suitable means, as by bolts 7 and 8, which pass through the base and extend up into the cylinder, the bolts being headless and having nuts 9 on their ends in order that they may be used as binding posts. I do not confine myself,'however, to this method of construction.

On the surface of the cylinder is a helical or spiral rib 10. The cylinder is wrapped with a conductor 11 of a suitable character, such as insulated or bare conducting wire or bare resistance wire. Where the inven tionis used in a variable resistance device, uncoated wire 1s preferably used, the turns being separated one from another. Where insulated wire is used, the portion of the wire passing over the top of the helical rib is scraped or cleaned in order to provide a good contacting surface. The opposite ends of the coil may connect with terminals 7 and 8, respectively.

Passing longitudinally through the center of the cylinder and rotatably supported thereby, is a shaft 12 which may carry an operating knob or dial, or other suitable operating member 13 on one end thereof.

Secured to the base by a bolt 14 is a spring contact member 15 bearing against a reduced end portion 16 of the shaft. The bolt 14, with nuts 14", provides a terminal for attaching a conductor, which conductor would then be in electrical connection with the shaft.

' In the shaft at eachend of the cylinder are holes 17 which slidably receive rods 18.

The outer extremities of the rods at one end are drilled to provide journals for reduced extensions 19 of a contact member 19 in the form of a roller. The roller 19 is preferably as long as the cylinder, or slightly longer. It is resiliently held in contact with the helical rib, or with the surface of the wires passing over the rib, by compression springs 20 surrounding the opposite end portions of rods 18, and confined between the shaft 12 and pins 21 in the outer ends of the rods.

When the shaft 12 is rotated, the roller is moved in a corresponding arc. As the roller,

contacts only with the portion of the wire that passes over the helical rib, it will progressively engage different turns of wire as it moves, that is, it will progressively cut in or out more turns of wire in a given circuit.

As an example, Fig. 7 may be referred to. Let point 7 in Fig. 7 correspond to terminal 7 of Figs. 1 to 3. In the same figure, 1] is the coil, and 19 is the roller. The contacting portion of each turn is indicated by a black dot at. It will be seen that as the roller 19 moves over the surface of the coil in the direction of the arrow, more turns of wire will be out into the circuit G. Fig. 7 is very much exaggerated, and in the construction shown in Fig. 1, the roller is always in contact with at least one turn of wire, so that the current may be gradually varied with out interrupting the current flow.

Fig. 8 shows the parts in the same relation as in Fig. 7, but designating its use as a potentiometer, the points 7 and 8 cor respondin'g to terminals 7 and 8, being connected to opposite sides of circuit G and roller 19 leading olf from an intermediate 'ometer, for use in connection with radio apparatus, the invention is in no wise limited to such 'use. The device shown might be a variable inductance device.

The invention may also be, adapted to devices carrying relatively heavy currents, such as rheostats for motors of any slze.

In heavier devices, the coil on the cylinder maybe in the form of a flat ribbon partly embedded in the cyllnder, such as the conductor 25 in Fig. 4. The coil might also be formed of heavy round stock 26, partially embedded, as in Fig. '5. It could also be in the form of a ribbon 27 turned edgewise as in Fig. 6.

Various other changes may be made 1n the construction of various parts to accord with the use to which the device may be put, within the contemplation of my invention and under the scope of the appended claims,

By reason of the, contact member 19 being a roller, the parts are subjected to very little wear.

I claim as my invention: 1. A variable contact device having two rincipalparts, one part-including a coil having an exposed spiral contacting surface, the other part including a rolling contact member extending co-axially with the axis of the coil and arranged to bear against a portion of the exposed spiral surface of the coil, one of said parts being movable relatively to the other whereby the point of contact between the coil and contact member may be varied.

2. Avariable contact device comprising a cylinder having a helically arranged rib on its surface, a conductor wound about the rods, said contact member crossing said rib and in contact with the conductor where it crosses the rib, the point of contact being relatively thereto, rods on theshaft at each end of the cylinder, a contact member comcylinder carried by said rods, said contact member crossing said rib and in contactwith the conductor where it crosses the rib, the

prising a roller extending lengthwise of the i point of contact being varied byrotating the shaft to move the contact member around the cylinder.

4. A variable contact device comprisin a cylinder having a helically arranged ri on its surface, a conductor wound about the cylinder, a shaft disposed along the central axis of the cylinder and rotatable relatively thereto, rods on the shaft at each end of the cylinder, a contact member comprising a roller extending lengthwise of the cylinder carried by said rods, said contact member crossing said rib and in' contact with the conductor where it crosses the rib, the point of contact'being varied by rotat ing the shaft to move the contact member around the cylinder, and means for resiliently urging the roller against the conductor. at its point of contact therewith.

5. A variable contact device comprising the shaft, one rod being located at each end of the cylinder, a contact member extending along the outside of the cylinder and supported by one end of each rod, and springs encircling the other ends of the rod and serving to yieldably hold the contact member in contact with the conductor at the point of intersection of the contact and rib, variation being effected by rotating said.

shaft to vary the point of intersection.

In testimony whereof I aflix my signa ture.

WALTER AMSLER. 

